(CNN) -- A group fighting for women's rights in Saudi Arabia condemned a judge Wednesday for refusing to annul the marriage of an 8-year-old girl to a 47-year-old man.

The group's co-founder, Wajeha al-Huwaider, told CNN that achieving human rights in the kingdom means standing against those who want to "keep us backward and in the dark ages."

The Society of Defending Women's Rights in Saudi Arabia, in a statement published on its Web site, called on the "minister of justice and human rights groups to interfere now in this case" by divorcing the girl from the man. "They must end this marriage deal which was made by the father of the girl and the husband."

The mother's lawyer, Abdullah al-Jutaili, said the judge found that the mother -- who is separated from the girl's father -- is not the legal guardian, and therefore cannot represent her daughter.

The judge requested, and received, a pledge from the husband, who was in court, not to allow the marriage to be consummated until the girl reaches puberty, al-Jutaili said. When she reaches puberty, the judge ruled, the girl will have the right to request a divorce by filing a petition with the court, the lawyer said.

Al-Jutaili said the girl's father arranged the marriage in order to settle his debts with the man, "a close friend" of his.

In its statement Wednesday, the Society of Defending Women's Rights in Saudi Arabia said the judge's decision goes against children's "basic rights." Marrying children makes them "lose their sense of security and safety. Also, it destroys their feeling of being loved and nurtured. It causes them a lifetime of psychological problems and severe depression.

"Moreover, children marriage creates unhealthy families because they were built on bad relationships."

The judge's decision also contradicts the king's consultative council, called the Majlis al-Shura, which found that anyone under the age of 18 "is a child and should be treated likewise," the women's rights group said.

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In an interview with CNN, al-Huwaider said the Saudi government has signed international agreements involving children's and human rights, "and they know that this is very harmful to the kingdom's image. There is a strong wave to teach and spread human rights here in Saudi Arabia, but we all know that there are two players behind the scenes: a movement that wants reform and change to better the kingdom and another movement that wants to keep us backward and in the dark ages."

Zuhair al-Harithi, a spokesman for the commission, said his organization is fighting against child marriages. "Child marriages violate international agreements that have been signed by Saudi Arabia and should not be allowed," he said.

Al-Harithi added that he did not have specific details about this case, but his organization has been able to stop at least one other child marriage.

Christoph Wilcke, a Saudi Arabia researcher for Human Rights Watch, said, "We've been hearing about these types of cases once every four or five months because the Saudi public is now able to express this kind of anger, especially so when girls are traded off to older men."

In an interview Wednesday with CNN, Wilcke said that while Saudi ministries may make decisions designed to protect children, "It is still the religious establishment that holds sway in the courts, and in many realms beyond the court."